Field of the Invention
The invention relates to a pressure fitting with a flow channel, a valve cone, a sliding element, and a locking device, wherein
a) the sliding element is disposed displaceably along a main axis of the pressure fitting; PA0 b) the valve cone is disposed on one end of the sliding element; PA0 c) the flow channel is closable by the valve cone; PA0 d) the locking element can be moved into a locking position, so that in a position of the valve cone that opens the flow channel the locking device engages the valve cone and/or the sliding element and keeps the valve cone in the position that opens the flow channel.
In all fields in technology in which containers or pipes are under pressure, pressure fittings are used, especially for pressure relief and pressure control. Pressure relief or pressure control can be accomplished both during normal operation and for safety of a system with components that are under pressure. Pressure vessels especially, under existing technical rules, must frequently be secured against overpressure. Moreover, in a pressure vessel, especially a steam boiler, the possibility of a pressure relief, even one to be initiated by hand, is demanded. By means of timely and sufficient pressure relief, the performance of flexible safety provisions can be improved. This is especially advantageous in a nuclear power plant with a primary system that is under pressure and that has components to be protected, such as the reactor core. A pressure relief of a pressure vessel which is under high internal pressure, an example being a nuclear reactor pressure vessel with an internal pressure of about 150 bar, to a pressure on the order of magnitude of an ambient pressure, of 2 to 4 bar, for instance, or to a pressureless state must be provided for, depending on the design specifications.
A safety valve for sealing off a hydraulic system that is under elevated pressure is described in British Patents GB 199 541 and GB 808 577. The safety valve is designed such that if a critical pressure is exceeded, a pressure reduction can be carried out. A common feature of both patents is that a structural embodiment of the safety valve is described in which by displacement of a locking element along an axis at right angles to the direction of the stroke of the valve piston of the safety valve, a locking of the valve cone in the position that opens the safety valve is attained. After an opening of the safety valve in accordance with specifications, or in other words after a critical pressure inside the hydraulic system is exceeded, the safety valve can be kept open down to a lower system pressure.
The locking element described in GB 808 577 is a ball, which is pressed into a groove of the valve piston via a piston that is prestressed by a spring. The piston that displaces the ball may be returned to its outset position either by a manually operated device or optionally by an electromagnetic device. In all cases, the locking element is embodied such that every time the safety valve opens, this safety valve is automatically kept open. Remote control of the locking arrangement is limited merely to returning the locking element or in other words re-stressing the spring.
The locking element described in GB 199 541 has two pins, disposed on opposite sides of a valve piston, which each engage a groove extending in the valve piston. The pins are pressed against the valve piston via a prestressed spring, so that force-locking engagement with the valve piston exists, preventing the piston from moving in its lift direction. If the pressure in the hydraulic system is so that both the frictional force of the pins and the force of the closing spring are overcome, then the piston is moved in the reciprocating direction. As soon as the respective grooves in the valve piston have reached the level of the pins, the pins are automatically pressed into the grooves in a manner that is not controllable from outside. Locking of the valve piston in a position that opens the valve is thereby attained. The prestressing of the springs of the pins can be regulated in such a way that at various system pressures, re-closing of the valve as a consequence of the closing force of the valve spring is attained.
Both GB 808 577 and GB 199 541 are limited solely to keeping a safety valve open with locking elements, which are moved along an axis at right angles to the reciprocating direction of the valve piston and which are put by a prestressed spring, without the possibility of influence (control) from outside, each time the valve opens into a position such that the valve piston remains in a position that opens the valve.
GB 808 577 discloses a fitting that includes a locking device. This device can be undone again only manually. German Patent Disclosure DE 597 161 discloses a fitting that can be locked with the aid of a pawl. The pawl is pressed into the closing position by a spring.
In those prior art fittings, the moving parts are powerfully accelerated and braked. This can be ascribed to the fact that they are not moved until there is a relatively high fluid pressure and are then locked abruptly.